Remove use of material-icons library from code base

[rtibbles]

Desired behavior

We should remove all mentions and usage of material-icons and replace with usage of Kolibri Design System icons where possible. Where not possible, we should just remove it (as in the base.html file).

Current behavior

We rely on an extra dependency for icons that has an unclear upgrade path.

[SukhvirKooner]

Hi @rtibbles,
I’d like to take on this issue. Could you clarify whether there are any specific guidelines or references for implementing Kolibri Design System icons? Also, are there any high-priority sections where this change should be made first?

Please assign this to me. Thanks!

[rtibbles]

Search for material-icons in the codebase would be the first start to identify places that need to be updated. Once you've identified what icons are being used, you can cross reference with https://design-system.learningequality.org/icons to see what icons we could replace them with.

It's also possible there are references where it is not being used at all, so we might be able to just remove at those points.

[SukhvirKooner]

Hi @rtibbles ,
I have raised the PR to replace material-icons with Kolibri Design System icons.
Let me know if changes are needed. Looking forward to your feedback!